Transcript Cell Structure and Function

Cell Structure and Function
Plasma Membrane
(Cell Membrane)
• Contains cell contents
• Double layer of phospholipids & proteins regulates the passage or
transport of certain molecules into and out of the cell, while
preventing the passage of others.
• Called Semi-permeable
Phospholipids
• Polar
– Hydrophylic head
– Hydrophobic tail
• Interacts with water
Nucleus
• Control center of cell
• Double membrane
• Contains
– Chromosomes
– Nucleolus
DNA
• Hereditary material
• Chromosomes
– DNA
– Protiens
– Form for cell division
• Chromatin
Nuclear Envelope
• Separates nucleus from rest of cell
• Double membrane
• Has pores
Nucleolus
• Most cells have 2 or more
• Directs synthesis of RNA
• Forms ribosomes
Cytoplasm
• Viscous fluid containing organelles
• components of cytoplasm
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Interconnected filaments & fibers
Fluid = cytosol
Organelles (not nucleus)
storage substances
Centrioles
• Pairs of microtubular structures
• Play a role in cell division
Endoplasmic Reticulum
• Helps move substances within cells
• Network of interconnected membranes
• Two types
– Rough endoplasmic reticulum
– Smooth endoplasmic reticulum
Rough Endoplasmic Reticulum
• Ribosomes attached to surface
– Manufacture protiens
– Not all ribosomes attached to rough ER
• May modify proteins from ribosomes
Smooth Endoplasmic Reticulum
• No attached ribosomes
• Has enzymes that help build molecules
– Carbohydrates
– Lipids
Mitochondria
• Have their own DNA
• Bound by double membrane
Mitochondria
• Break down fuel molecules (cellular respiration)
– Glucose
– Fatty acids
• Release energy
– ATP
Golgi Apparatus
• Involved in synthesis of plant cell wall
• Packaging & shipping station of cell
Golgi Apparatus Function
1. Molecules come in vesicles
2. Vesicles fuse with Golgi membrane
3. Molecules may be modified by Golgi
Golgi Apparatus Function
(Continued)
4. Molecules pinched-off in separate vesicle
5. Vesicle leaves Golgi apparatus
6. Vesicles may combine with plasma
membrane to secrete contents
Lysosomes
• Contain digestive enzymes
• Functions
– Aid in cell renewal
– Break down old cell parts
– Digests invaders
Cytoskeleton
• Filaments & fibers
• Made of 3 fiber types
– Microfilaments
– Microtubules
– Intermediate filaments
• 3 functions:
– mechanical support
– anchor organelles
– help move
substances
Pinocytic Vesicles
• Also called cell drinking
• Large pocket where large molecules such
as proteins and lipids, which cannot pass
through the cell membrane, will enter the
cell
• The edges close and pinch away forming
a bubble or vacuole in the cytoplasm.
Meiosis
• The process of cell division of the sex cell
or gamete
• When fertilization occurs, the two sex cells
combine to form a simple cell called a
zygote
Mitosis
• Divides into two distinct process
– Division of the nucleus
– Division of the cytoplasm
• Its an orderly series of steps by which the DNA in the
nucleus of the cell is equally distributed to two daughter
or identical nuclei
• Not all cells reproduce at the same rate:
– Blood forming cells in the bone marrow, cells of the
skin, cells of the intestinal tract reproduce
continuously.
– Muscle cells reproduce every few years.
Interphase
• “Resting Stage”
• An exact duplicate of each nuclear chromosome
is made (replication)
• At the start of mitosis, each chromosome has
already replicated and called a chromatid
– Joined by a structure called a centromere
• Two Centrioles are found in the Centrosome and
they replicate in preparation for next step
Prophase
• Two pairs of Centrioles start to separate
toward the opposite ends or poles of the
cell
– Microtubules form between them
– Nuclear membrane starts to dissolve
– Nucleolus disappears
– DNA becomes highly coiled
Metaphase
• Nuclear membranes completely dissolves
• Chromatid arrange themselves in a single
file
– Equatorial plate
Anaphase
• Chromatid pairs separate and pulled by
the spindle fiber toward the Centrioles
• Two chromatids or each replicated
chromosome are now fully separated
Telophase
• Chromosomes migrate to the opposite
poles of the cell
– They start to uncoil to become loosely
arranged chromatin granules
• Nuclear membrane and nucleolus
reappear to help reestablish the nucleus
as the definite organelle
– Two new daughter cells are formed
Molecule Movement & Cells
• Passive Transport
• Active Transport
• Endocytosis
(phagocytosis & pinocytosis)
• Exocytosis
Passive Transport
• No energy required
• Move due to gradient
– differences in concentration, pressure, charge
• Move to equalize gradient
– High moves toward low
Types of Passive Transport
1. Diffusion
2. Osmosis
3. Facilitated diffusion
Diffusion
• Molecules move to equalize concentration
Osmosis
• Special form of diffusion
• Fluid flows from lower solute concentration
• Often involves movement of water
– Into cell
– Out of cell
Solution Differences & Cells
• solvent + solute = solution
• Hypotonic
– Solutes in cell more than outside
– Outside solvent will flow into cell
• Isotonic
– Solutes equal inside & out of cell
• Hypertonic
– Solutes greater outside cell
– Fluid will flow out of cell
Facilitated Diffusion
• Differentially permeable membrane
• Channels (are specific) help molecule
or ions enter or leave the cell
• Channels usually are transport proteins
(aquaporins facilitate the movement of
water)
• No energy is used
Process of Facilitated Transport
• Protein binds with molecule
• Shape of protein changes
• Molecule moves across membrane
Active Transport
• Molecular movement
• Requires energy (against gradient)
• Example is sodium-potassium pump
Endocytosis
• Movement of large material
– Particles
– Organisms
– Large molecules
• Movement is into cells
• Types of endocytosis
– bulk-phase (nonspecific)
– receptor-mediated (specific)
Process of Endocytosis
• Plasma membrane surrounds material
• Edges of membrane meet
• Membranes fuse to form vesicle
Forms of Endocytosis
• Phagocytosis – cell eating
• Pinocytosis – cell drinking
Exocytosis
• Reverse of endocytosis
• Cell discharges material
Exocytosis
• Vesicle moves to cell surface
• Membrane of vesicle fuses
• Materials expelled
Disorders of the cell structure
• Cells may decrease in size- atrophy
– Due to aging or disease
• Cells may increase in size- hypertrophy
– Caused by an increase in workload
• Cells can increase in number- hyperplasia
• Cells have the ability to change into
another type of cell- metaplasia
– A protective response to a stimulus such as
smoking
Disorders of the cell structure
(continued)
• The change to the size, shape, and
organization of cells as a result of a
stimulus- dysplasia
• Then progresses to Neoplasia
– Change in the cell structure with an
uncontrolled growth pattern
Trauma or Injury
• Hypoxia- a decreased blood flow to
cellular structures
• Anoxia- a lack of oxygen flow to the
cellular structures
Tumor
• Results when cell division does not occur
in the usual pattern
– Also known as neoplasms
• Can be divided into two groups:
– Benign
– Malignant
Benign
• Composed of cells contained to the local
area.
– Other names: wart, papilloma
• Most can be surgically removed
Malignant
• Called cancer
• Continue to grow, crowding out healthy
cells, interfering with body functions and
drawing nutrients away from the body
tissue
• Can spread through a process called
metastasis
Symptoms of Cancer
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Changes in bowel or bladder habits
Sores that do not heal
Obvious changes in mole or wart
Unusual bleeding or discharge
A new lump or thickening in the breast or
elsewhere
• Difficulty in swallowing or frequent indigestion
• Persistent cough or hoarseness
How to detect
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X-ray
Mammogram
Sonogram
Biopsy